The present disclosure regards a stator or rotor of an electoral machine and also regards a method for twisting bar conductors, in particular for bar windings of electrical machines, and the related twisting apparatus.
Components of electrical machines are known, such as stators and rotors, which comprise bar conductors that are bent and connected together in different ways so as to make so-called bar windings.
In particular, belonging to the state of the art are bar windings made by means of bar conductors having a essentially rectangular cross section, where by rectangular it is intended both the square section and the “flat” section with which a section of rectangular shape is generally indicated. In such “flat” section, one of the two sides has lower size with respect to the other.
The aforesaid bar conductors are usually preformed by means of ‘U’-shaped or ‘P’-shaped bends, starting from straight bar conductors. The U.S. Pat. No. 7,480,987 describes a preforming method embodiment of bar conductors (in such document termed “hairpin conductors”). The preforming is such to modify the form of the straight conductors in a manner such that they can be suitably inserted in suitable radially aligned pockets made in a twisting device adapted to deform, after the insertion, the aforesaid preformed conductors. In practice, the twisting device essentially serves for “spreading” the legs of “U”-shaped or “P”-shaped form in order to ensure that two legs of a same conductor, after having extracted the latter from the twisting device, can be subsequently inserted in the slots of a stator or rotor core, radially offset from each other by a predefined pitch.
The United States patent application published with number US 2009/0178270 describes a method for twisting, with uniform pitch, preformed bar conductors after the insertion of the latter in the pockets of the twisting device.
The aforesaid twisting method makes the following steps:
the bending operation of the free end portions of the bar conductors (also called twisting from the welding side), after the insertion of such conductors in the slots of a stator core, and
the subsequent operation of welding together such bent, free end portions.
There is therefore the need to provide a stator or rotor that can be produced with an alternative twisting method to that described above, which simplifies the aforesaid operations of bending and welding of the free end portions of the bar conductors.